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Edelbrock Carb help needed
78 Chevyrado:
thoughts on the fuel pump.
https://www.youtube.com/watch?v=O-HWAccynrA
zieg85:
--- Quote from: 78 Chevyrado on October 09, 2024, 10:59:14 pm ---How long did it set between uses? I have a 1406 on my 78. If it sits more than 8 or 9 days its hard to start because all the gas has evaporated out of the bowls. I have an open type air filter. That lets it evaporate faster.
Could be an accelerator pump, but if all the gas has evaporated out of it the pump wont pump anything...
What is the time period between trys to start it?
If it starts today but not tomorrow.. theres a leak somewhere. if it starts today but not in a week, maybe a bad fuel pump letting the fuel run backwards back into the tank.
My 78 always had fuel pump problems, every 6 months. I always bought the store brand fuel pumps for $20 to fix it. it would work great for 6-8 months. turns out it was cheap fuel pumps. I bought an Edelbrock #1721 fuel pump for oh about $140 or so 6 years ago... I know people say my stock 350 doesnt need that and I agree. ECEXPT.. that pump has been good for the last 6 years. no failures. My stock 78 engine has a bunch of hotrod parts on it. not because i think they are cool. but because I got tired of buying and replacing the cheap parts every year. the edelbrock pump has worked out for my beautifully. the normal $25-$55 pumps are all cheap garbage. buy the Edelbrock and be done with it.
That I will spend on necessary extra on parts like that is why my truck is so reliable. you can buy one edelbrock pump for $160 and be done with it or you can buy a $25 pump every 8 or 9 months. I figured out I need my truck to work when I need it not when it feels like it.
--- End quote ---
A little update. After 2 weeks of sitting the fuel filter is still full. What made the most sense to me is the carb is dry after a few days. I will crank it a little to get the carb filled with fuel again then start pumping it to set the choke and it will take off. This points to the carb leaking down to me. It is real close to the time to put it away for a winter's nap anyway and depending on what else happens in life I have big plans to convert it to PDB and a manual transmission to get it more enjoyable to drive. Thanks Kenny!
78 Chevyrado:
When my 78 has sat too long and The fuel has evaporated out of the bowls it take a good 20+ seconds of cranking to make it light off. Before that with the crap fuel pumps, it would take 40-50 seconds to pull fuel from the tank to the pump and then to the engine and fill the bowls enough to run. if it starts in less than 10 seconds or so after 2 weeks of sitting you must have a closed air filter or a better filter than I do. When I used to have the old clear fuel filters, It would stay full looking for 1.5 months or so.
To the original post. If you have a bad accelerator pump. It will stall when you blip it because you suddenly have way too much air for the mixture. the AP squirts a shot of fuel in there to make that difference up. even if set up poorly, it should squirt enough fuel to keep it from dying/stalling out.
Easiest way to check your accelerator pump is to make sure the bowl is full. With engine off, look down the throttle primary bores (you'll see the tubes above the venturis) and hit the throttle (give it a full pump by hand) full while looking down there. you should see an obvious BIG squirt of fuel on the left and right side.. if you don't see that big squirt of fuel accelerator pump is bad or weak. The big squirt should also be about equal from left to right side venturi. If they are not equal that is a problem too as in there is dirt in something. that means you need to fully disassemble the carb and clean it. if its had too much gas evaporate too many times it may be dirty. When the gas evaporates the volatiles of the fuel go away but not the solids. if you let it evaporate off too much you will get a build up of those solids and have to disassemble the carb and clean off those solids.
Edelbrocks, the way they're made, the fuel bowls cannot leak into the engine because the entire bottom half of the carb is one piece. no gaskets to fail. not like a Holley with gaskets top and bottom of valve body. either fuel is being sucked out the venturis into the engine or its all evaporating out of the bowls. an open air cleaner vs a stock one, the open one will dry up faster.
The clear fuel filter looking full is not an indication there is fuel in there. Ignore that. the filter may be full and (looking like it's) holding some fuel but the lines before it and after it are dry and have air in them.
JohnnyPopper:
Years ago (45?) there was an inline spring loaded ball check valve for sale. 3/8?
Can't recall a brand
I do recall by placing it inline before the carb solved many issues listed on this thread,i.e. worn out diaphragm/fuel pump plunger/weak failing Fuel pump
Picture this: somewhat charged or decent battery, combined with a tired starter-slow turnover of a tired fuel pump...fuel coming from the tank? or maybe between the tank and fuel pump...= SLOW
I'm sure Bill Cosby could elicit the sound of the chaos... 8)
It might be old school, but keeping fuel in the line closest to the carb makes the most sense to me.
Interestingly I bought a new battery from Cco and it didn't affect the starter performance. Thinking the battery was a dud, exchanged, only to find the 'Starter' was the worn out piece. When starting now, I turn the motor over while pumping the pedal.
According to GM instructions, one pedal pump is needed to fire up a Rochester enabled engine. I am here to attest, that, in the well defined and practically implemented tuning measures, one slight tap on the gas pedal is enough to fire her up...
Inline check valve in place, within 1 minute or significantly less, fuel is present in the accelerator and she blazes!!!
All that said, the variables are many: battery/starter condition; fuel pump pressure/volume; carb accelerator pump condition or lack there of...
I'd start with an inline one-way check valve close to the carb. At least you will eliminate a few questions off your list.
Mr Diesel:
I like the one-way ball check valve idea. I had experimented with this before for similar issues in fuel lines but ultimately abandoned it because of inferior one way valves (plastic with seam=leaky). Your post got me thinking about this again so I went digging on Ebay for something sturdier and still cheap. Found a 3/8" ball check valve with no leaky seam or joint, intended for the high pressures of hydraulic fluid. Might need a spring modification inside but looks like it comes apart easily enough. I ordered one and will take a look at it when it arrives:
Hydraulic Check Valve: 3/8” x 3/8” Male NPT, Inline Ball Valve | 82663-06
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